Force vector direction control

ABSTRACT

A settable control to maintain a selected resultant force vector of lift and pull cylinders of a fluid system operated walking mechanism for heavy equipment, which control has members to simulate the forces and movements of the lift and pull cylinders joined by a floating pivot to a vector control lever which opposes movement of the floating pivot along the longitudinal axis of the control lever. Movement of the pivot in other directions by the force-simulating members operates a valve control for the fluid system to maintain the selected force vector.

United States Patent Baron Mar. 14, 1972 [54] FORCE VECTOR DIRECTION CONTROL [72] Inventor: George B. Baron, RD. 4, Marion, Ohio [22] Filed: Feb. 6, 1970 [2]] Appl. No.: 14,692

Related US. Application Data [62] Division of Ser. No. 698,590, Jan. 17, 1968, Pat. No.

[52] US. Cl ..91/l76,91/217, 91/420 [51] Int. Cl ..F0lb 15/02, F15b11/08, F15b 13/042 [58] Field ofSearch ..91/363 A,217,420, 176

[56] References Cited UNITED STATES PATENTS 3,190,185 6/1965 Rasmussen ..91/363A Ross ..91/217 Westbury et al ..91/217 Primary Examiner-Paul E. Maslousky Attorney-Mason, Fenwick & Lawrence [57 ABSTRACT A settable control to maintain a selected resultant force vector of lift and pull cylinders of a fluid system operated walking mechanism for heavy equipment, which control has members to simulate the forces and movements of the lift and pull cylinders joined by a floating pivot to a vector control lever which opposes movement of the floating pivot along the longitudinal axis of the control lever. Movement of the pivot in other directions by the force-simulating members operates a valve control for the fluid system to maintain the selected force vector.

5 Claims, 9 Drawing Figures atemed 14, 972

5 Sheets-Sheet 1 Patented March 1%,, IQWZ 5 Sheets-Sheet 3 1 Pmwwed Mam-ch l4, 1%72 5 Sheets-Sheet 5 Patented March H mm 5 Sheetssheet 4 FORCE VECTOR DIRECTION CONTROL REFERENCE TO PRIOR APPLICATION This application is a division of copending application Ser. No. 698,590, filed Jan. 17, I968, WALKING MECHANISM AND CONTROL THEREFOR, George B. Baron, inventor, now U.S. Pat. No. 3,5l2,597.

BACKGROUND OF THE INVENTION This invention relates to walking systems for heavy equipment and to controls therefor, and particularly to hydraulic walking systems and to means for fixing and/or controlling the resultant forces of the cylinder systems making up such a walking system.

Some heavy equipment, particularly excavating machinery such as is used in mining operations, has been provided with shoes at each side to walk them as work progresses. The mechanism for operating the shoes has been mechanical in nature, and as the capacity and weight of the machines have increased, the proportions of the shoe operating mechanism has necessarily become larger. A point has been reached where the weight and size of the moving mechanical parts are so great that manufacture and practical operation are becoming increasingly difficult, and no way has been discovered to split the loads so that they could be carried by a multiplicity of small components.

Another disadvantage of the mechanical system is the necessity of lifting the leading edge of the base, or tube, of the machine a considerable distance above the earth each step, to insure enough height to move over obstacles, or rises in ground, and this is more than required for most moving steps. The lift of the leading edge causes the trailing edge to dig in and drag heavily and accumulate a pack, or roll, of dirt, which clings to the bottom. If the ground is high under one shoe, that shoe will take its full load before the other shoe begins to take a load. This requires much heavier and more complex structure in the machine to withstand unbalanced loading conditions. Also, as the first loaded shoe begins to move the machine, it causes a sudden rotation of the machine about its vertical axis, which has been known to cause undesirable bending stresses in the boom.

Some work has been done with hydraulic operating mechanism for the shoes, but problems of control to achieve practical operation under all conditions have not previously been solved.

Due to the tremendous weight of the machine being walked, it is desirable to lift the weight only so much as is necessary to permit sliding the base, or tub, on which the machine rests. Nevertheless, it is necessary at times to raise the leading end of the base a sufficient height to move over an obstruction, or rise in ground. Thus, a system is required which will allow variations in step pattern if optimum efficiency is to be obtained, and this, in turn, calls for a flexible control device which will cause variation in step pattern.

SUMMARY OF THE INVENTION The general object of the present invention is to provide a control to determine and maintain a desired resultant force direction applied to the walking shoes of hydraulically operated walking mechanism.

Another object is to provide such a control having means for fixing and/or controlling the direction of the resulting force vector of two systems of hydraulic cylinders whose operating angles vary constantly.

A further object is the provision of a control of this nature having a settable lever connected to a shiftable pivot to resist movement of the pivot in a direction lengthwise of the lever, with other means responsive to the movements and forces of the two hydraulic systems also connected to the pivot to shift the pivot in directions at right angles to the lever length to control a valve and regulate movement of the cylinders of the two systems.

Other objects of the invention will become apparent from the following detailed description of one practical embodiment thereof, when taken in conjunction with the drawings which accompany, and form part of, this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of the base portion of an excavating machine, such as a dragline, equipped with walking shoes which are operatively connected to the machine by means of the hydraulic system of the present invention;

FIG. 2 is an end view of the structure shown in FIG. ll;

FIG. 3 is a partial top plan view of the structure shown in FIG. ll, only one shoe being shown;

FIGS. 4A, 4B and 4C show successive positions of the shoe in making a step;

FIG. 5 is a diagrammatic view of the hydraulic system, only the arrangement for one side of the system being shown;

FIG. 6 is an elevational view of the vector control mechanism; and

FIG. 7 is a section taken on the line 7 -7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1, 2 and 3 of the drawings, there is shown a portion of a dragline excavating machine 1 having a base, or tub, 2 which seats upon the ground and rotatably supports a platform 3 upon which the machinery is mounted. The usual boom 4 has its foot connected to the platform 3.

At each side of the machine, there is a shoe 5 suspended from the platform by hydraulic cylinders 6. The cylinders are attached to the platform by ball joints 7, and their piston rods are connected to the shoes by ball joints 8. For purposes of this disclosure, these cylinders will be termed lift cylinders. In the embodiment shown, they raise and lower the shoes, and lift the weight of the machine when the shoes are in contact with the ground and the machine is to be moved. There is one, or more, cylinder 9, pivotally connected to the platform at 10 with its rod connected to the shoes at 11, which cylinder will be termed a pull cylinder, for it moves the machine longitudinally of the shoes when the weight is on the shoes. A third set of cylinders 12 are pivotally connected to the platform and shoes and control the side thrust imposed when moving over uneven terrain. The cylinders 12 are necessary for stability, but their operation and control are not part of the present disclosure.

Although four lift cylinders 6 have been shown connected to each shoe, the system is not limited to the use of this number of cylinders, nor to the specific arrangement of cylinders shown. All of the cylinders must be so located, and so connected to the respective components, as to permit universal movement of the shoes so that they may adapt themselves to ground contour.

The various operations of the lift cylinders 6 and the pull cylinder 9 are controlled by a hydraulic system (See FIG. 5) and the step movement is determined by operation of a vector control 13 (See particularly FIGS. 6 and 7).

The hydraulic circuit diagram shown in FIG. 5 discloses only one side of a complete system except for an equalizing valve 14 and a relief valve 15 which serve both sides of the system. The system shown would be for a relatively small machine, as each side is driven by a single pump 16. The pump is of the reversible displacement type, and its stroke control is linked mechanically, or otherwise, to that of the other pump, so that the displacement of the two pumps is always the same. Although the pump 16 is reversible, for purposes of disclosure the line 17 leading from the pump will be referred to as the outlet line and the line IS the inlet line. Lines 19 connect the several lift cylinders 6 in parallel to the outlet line I7, while line 17 continues to the equalizing valve 14. An oil supply line 20 connects to line 17 and leads from tank 21. A check valve 22 is in line 20 to permit flow from the tank only. A second line 23 leads from the check valve to the inlet line 18 to control the check valve when the pump is operating in a reverse direction and pressure in line 18 exceeds a predetermined amount. The rod ends of cylinders 6 are connected in parallel by lines 24 to a line 25 which extends to the other side of the system. Relief valve is connected into line and empties into tank 26. A branch line 27 runs from line 25 to a tank 28, and is controlled by a manually operable valve 29. A branch 30 from line 27 is connected to a pressure operated valve 31, which is controlled by a line 32 from one of the lift cylinder feed lines 19. Lines 33, from the rod end of pull cylinder 9, 34, from inlet 18, and 35, to a tank 36, are also connected to valve 31. The piston end of cylinder 9 is connected by line 37 to pump inlet line 18, and by a branch 38 from line 37 to valve 39 of the vector control 13. There is a check valve 40 in line 37, between lines 18 and 38, operable to permit flow toward cylinder 9, and a line 41 from a tank 42 supplies line 18 when needed under control of a check valve 43. Line 18 and a branch 44 from line 25 also are connected to the valve 39. A line 45 from the equalizer valve 14 to line 33 completes one side of the system, the other side being a duplicate. it will be understood that while separate tanks 21, 26, 28, 36 and 42 have been illustrated for purposes of convenience, these are in fact symbols of a single tank.

Vector control 13 is shown in detail in FIGS. 6 and 7 of the drawings. It consists primarily of three pivotally interconnected levers, with two of them being of variable length to enable shifting of the point of interconnection, and the valve 39, which is controlled by movement of the point of lever interconnection. The three levers are a vector lever 46, a lift cylinder lever 47, and a pull cylinder lever 48. The levers 47 and 48 are miniature cylinders having predetermined pressure ratios proportional to the pressure ratio between all of the cylinders 6 and all of the cylinders 9. Vector lever 46 has its outer end connected to a rod 49, which may extend to a hand operated, or mechanically operated, control (not shown) while lever 47 is connected to an extension 50 of a lift cylinder 6 by rod 51, and lever 48 is connected to an extension 52 of the pull cylinder 9 by means of rod 53. The respective extensions and levers, and their respective pivotal points and pivotal connections to the connecting rods, form parallelograrns to maintain parallelism between lever 47 and cylinder 6 and lever 48 and cylinder 9 at all times. Vector lever 46 represents the direction of resultant force of all cylinders on one side of the machine.

The three levers are mounted for arcuate movement about their common connection 54 by means of rollers 55, 56 and 57, movable along an arcuate slot 58 in a mounting board 59. Lever 47 is composed of a small cylinder 60 having an extension 61 at one end carrying the roller 56 and connected to rod 51. The rod of the cylinder is connected to the common connector 54. Lever 48 includes the small cylinder 62 with extension 63 on which roller 57 is mounted and to which rod 53 is joined. Roller 55 is mounted on the vector lever 46.

Control cylinder 60 has its head end in communication with the head end of one of the lift cylinders 6 (preferably one near the center of the shoe for most accurate response when the shoe is in a tilted position) through hose line 64, and its rod end in communication with the rod end of the same cylinder by hose 65. Hose lines 66 and 67 similarly connect cylinder 62 with a pull cylinder 9. Thus, the pressures in the control cylinders 60 and 62 will be the same as those in the lift and pull cylinders. The control cylinder pressures are balanced, however, when the pressures in the operating cylinders are proper for the step form being followed, so that there will be no retractive or extension movements of the control cylinders unless the selected resultant force vector is not being followed. Therefore, the strokes of the control cylinders 60 and 62 are not proportional to those of cylinders 6 and 9. As vector lever 46 is of set length, only forces effective perpendicularly to the vector lever axis will result in movement of the common connection 54 to the right or left (as viewed in FIG. 6). These movements are transmitted to valve 39 by link 68 connected to the common connection and the valve stem. Movement of the connection 54 to the left corresponds to downward movement of the valve symbol 39 in the diagram of FIG. 5. In both FIGS. 5 and 6 this movement compresses spring 69. The return spring 69 must have a sufficiently high rate to stabilize the servosystem, thus allowing some error in the vector direction. In order to minimize the error, cylinder 60 could be tipped a little to the right with respect to the lift cylinders, or some other kind of known bias could be built into the system.

In operating the apparatus to move the machine to which it is attached one step, the shoe is first dropped from its raised, parked position, as shown in FIG. 4A, into contact with the ground, as shown in FIG. 4B. This can be done by opening valve 29 momentarily to allow discharge of oil from the rod ends of cylinders 6 into the tank, or the shoe may be pumped down by beginning oil delivery from pump 16 into outlet line 17 and cylinder head lines 19, in which case oil from the rod ends of cylinders 6 flows through lines 24, 27, 30, valve 31, line 34 and inlet line 18 to the pump. Excess oil required to fill the cylinders 6 comes from the tank 21 through replenishing pilot check valve 22. After the shoe touches the ground, oil may flow to the system on the other side of the machine through the equalizing valve 14, unless the other shoe is already on the ground, in which case pressure begins to build up in all of the lift cylinders on both sides simultaneously. Pressure in the lines 19 is imposed upon the block of valve 31 through line 32, and a small pressure will cause the block to shift, thus isolating the rod end of the pull cylinder 9 and opening the rod ends of the lift cylinders 6 directly to the tank 36. When the pressure or, more correctly, the sum of the pressures, reaches the setting of valve 14, which may be about two-thirds of the pressure required for walking, valve 14 shifts and isolates the systems at the two sides of the machine, and at the same time connects the rod end of the pull cylinder in parallel with the head ends of the lift cylinders.

With vector control valve 39 in the position shown, no oil can flow from the head end of the pull cylinder 9 and no pull can be developed. However, such a condition would cause an increase in pressure in the head end of the pull cylinder 9, which pressure increase will be transmitted to the head end of control cylinder 62 of lever 48 and increase that lever length and cause the vector link 68 to move to the left (as viewed in FIG. 6), thereby shifting valve 39 to the next block, so that oil can flow from the head end of pull cylinder 9 through pipe 38, valve 39 and pump inlet line 18. At the beginning of the step, all pistons would be retracting, thus decreasing the system volume so that more oil would be coming out of the pull cylinder 9 than going into the pump 16. Therefore, the inlet pressure would tend to increase without limit, thus continuing to prevent any pull from developing. Further movement of the vector link 68 to the left would then take place, so that valve 39 would shift to the last block, and excess oil would return through line 18, valve 39, lines 44, 25, 27, 30, valve 31 and line 35 to tank 36. This return would be at no pressure and the pull of cylinder 9 would be maximum. Since the cylinders and walking geometry will be so proportioned that the required pull is always somewhat less than maximum, it can be seen that valve 39 would never become fully open to the tank, but would seek a position where the excess oil would be throttled at just the right pressure to keep the vector link 68 in balance. Therefore, the resultant of the lift and pull cylinder forces remains in the desired direction and the machine tub is pulled forward.

As the step progresses, the lift cylinders 6 go over center and begin to extend (See FIGS. 43 and 4C). The required pull diminishes because the machine weight is assisting in the movement and reaches zero when the lift cylinders 6 are parallel to the vector. Finally, the required pull becomes negative (in other words, a push). The rod diameter in the pull cylinder 9 will be so selected that only in the last small fraction of the step does the system volume under pressure begin to increase. When this happens, less oil is coming out of the pull cylinder 9 than is going into the pump, the difference coming out of the tank through replenishing check valve 43, so that the inlet pressure is zero. In order to maintain equilibrium on the vector link 68, valve 39 gradually shifts back toward the position shown, where it closes just enough to maintain the desired pressure by throttling the cylinder discharge.

The reason for staging valve 39 into both the pump inlet and the tank is to conserve hydraulic power. If this valve controlled flow only to the tank, all of the power taken away from pull cylinder 9 would be wasted.

When the step is completed, the pump discharge is stopped. There could be a limit switch, or other device, on the pull cylinder on each side of the machine, so that step completion on either side would stop the discharge of both pumps.

After the step is completed, the operator would move the delivery control so that oil would flow through the pump in the opposite direction, and the pressure on the head ends of the lift cylinders would begin to reduce. Momentarily, the discharge would go into the head end of the pull cylinder 9, but if the pressure increased very much there, the vector link 68 would move to the left and shift valve 39 to the last block so that the line would be open through valve 39 to the tank 36. When the sum of the pressures from the two sides is reduced to the setting of valve 14, that valve shifts back to the position shown, thus permitting the two sides to equalize and disconnecting the rod end of the pull cylinder from the lift cylinders. When the pressure finally becomes negligible, valve 39 shifts back to the position shown, so that the rod ends of the lift and pull cylinders, as well as the overflow port of valve 39, are connected to the pump discharge. Valve 39 will then be inoperative. As discharge pressure begins to build up, pilot check valve 22 is forced open, so that the head ends of the lift cylinders 6 are connected to the tank 2i.

At this stage of the movement, the lift cylinders are exerting a forward force on the shoe, and the pull cylinder, with its large rod acting as a ram, is exerting a forward push. The resultant of these forces is in such a direction that the shoe must slide on the ground in the same manner as the tub slid during the step. However, the vector direction is not fixed. Therefore, the rod size of the lift cylinders must be large enough so that the resultant stays well ahead of the vertical direction when the shoes approach the starting position, or else they will leave the ground prematurely Also, the shoes should be so balanced that they are heavy at the right-hand end, so that the other end will not dig in.

When one shoe reaches the starting position, its pull cylinder 9 is fully extended and can exert no more push. Therefore, the effective piston area acting on the shoe becomes smaller and the pressure tends to rise. Since the pump discharges are connected across the machine, the flow can be diverted to the other side to speed up the return of that shoe. When both shoes are at the starting position on the ground, the pressure would rise as they begin to lift. This rise can be used as a signal to reverse the pump and begin another step, as already described, except that it starts with the shoes on the ground. On the other hand, the operator may decide to park the shoes, in which case further pumping to the right will simply raise them from the ground until all lift cylinders are bottomed, the pull cylinders remaining fully extended. The resulting dead-end condition can be relieved either by valve or by suitable known pump controls.

One reason for pressurizing both ends of the pull cylinder on the return stroke is to obtain greater return speed without requiring greater pumping capacity. It is not necessary to use vector control on the return stroke as the vector direction is not critical as it is during the step. The shoes are so light relative to the machine that there is no possibility of sliding the tub instead of the shoes during the return stroke if the vector stays above the horizontal direction.

While in the above one practical embodiment of the invention has been disclosed, it will be understood that the details of construction shown and described are merely by way of illustration and the invention may take other forms within the scope of the appended claims.

I claim: 1. Means for controlling the resultant force vector of two angularly related systems of elongatable members whose angles vary continuously comprising, a settable vector control means, means to oppose the vector control means responsive to the resultant force vector of the two systems of elongatable members and connected to the vector control means by a floating connection, whereby changes in angle of the resultant force vector will move the floating connection, and means responsive to movement of the floating connection to control elongation of one of the two systems of elongatable members.

2. Means for controlling the resultant force vector of two angularly related systems of elongatable members whose angles vary constantly as claimed in claim 1 wherein, the means to oppose the vector control means includes separate means maintained in parallelism and under proportional forces respectively with the elongatable members of the two systems.

3. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly comprising, a vector control lever, a first control cylinder connected at one end to one of the fluid cylinders of a first one of the systems to maintain parallelism with the cylinders of the first system and in fluid communication with the cylinders of the first system to maintain a force proportional to that of the first system, a second control cylinder connected at one end to one of the cylinders of the second of the systems to maintain parallelism with the cylinders of the second system and in fluid communication with the cylinders of the second system to maintain a force proportional to that of the second system, the other ends of the first and second control cylinders and one end of the vector control lever being interconnected by a common floating pivot, whereby the resultant force of the first and second control cylinders will cause movement of the floating pivot unless the resultant force is longitudinally aligned with the vector control lever, and means responsive to movement of the floating pivot to control operation of the cylinders of one of the two systems.

4. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly as claimed in claim 3 wherein, there is a mounting member, the first and second control cylinders and the vector control lever extend radially from the floating connection, and there are means mounting the first and second control cylinders and the vector control lever on the mounting member for angular movement about the floating pivot.

5. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly as claimed in claim 4 wherein, there are means to change the radial positions of the vector control lever to change the resultant force direction of the cylinders of the two systems. 

1. Means for controlling the resultant force vector of two angularly related systems of elongatable members whose angles vary continuously comprising, a settable vector control means, means to oppose the vector control means responsive to the resultant force vector of the two systems of elongatable members and connected to the vector control means by a floating connection, whereby changes in angle of the resultant force vector will move the floating connection, and means responsive to movement of the floating connection to control elongation of one of the two systems of elongatable members.
 2. Means for controlling the resultant force vector of two angularly related systems of elongatable members whose angles vary constantly as claimed in claim 1 wherein, the means to oppose the vector control means includes separate means maintained in parallelism and under proportional forces respectively with the elongatable members of the two systems.
 3. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly comprising, a vector control lever, a first control cylinder connected at one end to one of the fluid cylinders of a first one of the systems to maintain parallelism with the cylinders of the first system and in fluid communication with the cylinders of the first system to maintain a force proportional to that of the first system, a second control cylinder connected at one end to one of the cylinders of the second of the systems to maintain parallelism with the cylinders of the second system and in fluid communication with the cylinders of the second system to maintain a force proportional to that of the second system, the other ends of the first and second control cylinders and one end of the vector control lever being interconnected by a common floating pivot, whereby the resultant force of the first and second control cylinders will cause movement of the floating pivot unless the resultant force is longitudinally aligned with the vector control lever, and means responsive to movement of the floating pivot to control Operation of the cylinders of one of the two systems.
 4. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly as claimed in claim 3 wherein, there is a mounting member, the first and second control cylinders and the vector control lever extend radially from the floating connection, and there are means mounting the first and second control cylinders and the vector control lever on the mounting member for angular movement about the floating pivot.
 5. Means for controlling the resultant force vector of two angularly related systems of fluid cylinders whose angles vary constantly as claimed in claim 4 wherein, there are means to change the radial positions of the vector control lever to change the resultant force direction of the cylinders of the two systems. 